Using its UQC underwater telephone, the Seawolf requested the Thresher turn its beacons on and off. A few minutes later, Seawolf reported “We hear what may be interrupted keying now,” suggesting the beacons were now being switched on and off deliberately.
The Seawolf faced a problem, however, since the sonar activity of the destroyers that were also involved in the search was making it hard to decipher signals coming from what was now assumed to be the Thresher. Furthermore, the Seawolf needed to come near the surface each time its crew wanted to relay messages to other vessels in the search party, or to the headquarters ashore.
A second dive by the Seawolf involved another attempt to communicate with the Thresher. “If you hear my transmission, key your underwater telephone,” was the message sent using the UQC.
At 1:55 PM, the Seawolf reported that it received the emergency beacon tone three times. Five minutes later, another two tones were heard. As of this point, and if the Seawolf report is indeed correct, it seems certain that there were at least some people still alive on the Thresher. While it’s unclear what depth it was at, its hull had obviously not fully collapsed.
What appears to be conclusive evidence then came to the crew of the Seawolf at 2:15 PM, when they heard the main sonar from the Thresher, indicating that there were not only survivors aboard the submarine, but that it still had enough power reserves to transmit actively.
At 2:24 PM the report notes that the sonar on the Thresher stopped transmitting, likely after the battery became exhausted. In total, the Seawolf had heard no fewer than 37 pings from the sonar of what it identified as the stricken submarine.
At 2:33 PM, the Seawolf reported it “may hear [a] very weak voice” over the Rycom receiver, but the communications were too garbled to make sense of.
On the third dive, the sonar operators on the Seawolf said they began to hear the telltale banging of metal upon metal, suggesting that someone aboard the Thresher was trying to make contact. “Bang five times on hull,” was the request made by the Seawolf.
Although the Seawolf did not get the five bangs requested, and instead heard groups of three, it did successfully make active sonar contact again, followed by more raps on the hull that were detected at 8:30 PM.
Once again, the Seawolf needed to surface to issue a report, and once again it broke any contact with the Thresher.
A fourth and final effort to find the missing submarine was then made early in the morning of April 12, almost two days since the Thresher had first been posted as missing.
Trying the active sonar and calling the Thresher again on UQC yielded no response. “No answers, no signals,” in the words of the report from the Seawolf. At 5:52 AM the dive was ended.
Eventually, of course, the remains of the Thresher were located on the seafloor at a depth of 8,400 feet. But what happened in the lead-up to this catastrophe is now far less certain. At least, the original narrative that had the submarine rapidly sink at the point at which communications were originally lost, seems to be erroneous.
While the Navy was compelled to release these new documents, it remains perplexing as to why aspects of this report, at least, were never disclosed before. Previously, the official line was that the Navy thought the Thresher underwent an implosion, which would have made any survivors of the initial accident a near-impossibility. In the meantime, the issue of what actually happened has continued to be controversial and now the official narrative has only become more contested.
In his analysis, Amick suggests it might have been a case of the Navy wanting to keep the prolonged demise of the Thresher a secret from the families of those who died. Whatever the reason, we are now, slowly, finding out more about this naval tragedy — the second-deadliest submarine incident on record — but there are clearly many unknowns that remain.
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